Absorbent element for filters and the like



Nov. 12, 1957 R. MacHENRY ABSORBENT ELEMENTFOR FILTERS AND THE LIKEFiled May 17, 1955 United States Patent ABSORBENT ELEMENT FOR FILTERSAND THELIKE Richard MacHenry, Prospect Park, Pa., assignor to AmericanViscose Gorporation, Philadelphia, Pa., a corporation of DelawareApplication May 17, 1955, Serial No. 509,000

28 Claims. (Cl. 131-10) The present invention relates to porous orsponge-like elements of synthetic fibers and" more particularly to animproved fil'ter suitable for cigarettes.

Tobacco: smoke is made. up of a. mixture of gaseous compounds and finelydivided solids, for example, tar, phenol, acetic acid, a'crolein, carbondioxide, water vapor, and dust particles. These compounds and elementsare formed and derived from the disintegration of the tobacco and, inthe case of cigarettes, the paper wrapper. While cigarette filters havebeen known in the past and used to a certain extent, the necessity forproviding an adequate filter and the shortcomings of previous filtershave only recently been appreciated. The requirements fora satisfactorytobacco smoke filter are, first, that it eflfectively remove toxic orharmful ingredients from the smoke drawn into the users mouth. Secondly,the filter must be sufficiently porous so. that. it does not interferewith free passage of the smoke or what is commonly termed the draw. Inaddition, a cigarette filter must be sulficiently firm to support thecigarette without bending or becoming undesirably soft and flabby. Itwill be appre elated from the above requirements that good draw isordinarily inversely proportional to filtering ability, namely, thedenser the filter, the more effective is the filtering, but suctionrequired to draw the smoke through the filter is al'so'highen. Due tothe peculiarly beneficial structure resulting from a uniform mixture ofa major proportion of crimped staple fibers and a minor proportion ofpotentially adhesive'fibcrs which serve to bond the mixture together, Ihave been able to produce a filter which approaches the desired resultsof maximum filtering combined with easy draw.

A primary object therefore of the invention is to provide a fibrouselement of high porosity and absorbency.

A further object of the invention is to provide: an internallyboundffirm' bodied, absorbent element of uniform rigidity for medicalandsurgical uses. 1

A still further object ofthe invention is to provide a tobacco smokefilterhaving. maximum filter effectiveness and maximum draw.

A still further object. of the invention is to provide a tobacco smoke;filter made up of a fiber bonded mixture of non-adhesive textile fibersandpotentially adhesive fibers to form a porous filtering element.

A still further object of theinvention is to provide a tobacco smokefilter made up of a mixture of. crimped non-adhesivetextile fibers andpotentially adhesive textile fibers bonded together to form a porousfiltering. element.

2,812,767 Patented Nov. 12, 1957 Another object of my invention is toprovide a filter of the above objects which filter has numerous minutetraps for the entrappiug of the components of the smoke passing throughthe filter.

' Another object of my invention is to provide a tobacco smoke filterwherein the filtering efficiency increases during use.

Still a further object of my invention is to provide a tobacco'smokefilter which may have incorporated therein additional substances such asperfume, menthol or other additional desired or essential oils.

Still another object of my invention is to provide tobacco smoke filtersof varied color.

It is still another object of my invention toprovide a filter typecigarette incorporating therein the filter of the above objects.

Further objects will be apparent from the specification and drawing inwhich:

Figure 1 is a perspective of my improved porous element;

Figure 2 is a perspective showing a cigarette filter plug formed fromthe element of Figure 1;

Figure 3 is a perspective showing the filter" plug of Figure 2incorporated in a cigarette;

Figure 3A is a magnified view of the fibrous filter element showing indetail the interrelationship ofthe fibers in greater detail;

Figure 4 is a schematic sectional view of the apparatus for fabricatingmy improved porous elements; and

Figure 5 is a fragmentary detail on an enlarged scale as seen at VV ofFigure 4.

Briefly the improved absorbent element, which is useful either as atobacco smoke filter or as an absorbent pad for medical and surgicalpurposes, comprises a uniform mixture of crimped, non-adhesive textilefibers of relatively low denier and potentially adhesive textile fiberswhich have been secured to the non-adhesive fibers by rendering theinitially potentially adhesive fibers tacky. A major portion of themixture is composed of the non adhesive fibers which are previouslycrimped and of staple length. The mixing of the fibers is efiected whenthe potentially adhesive fibers are in a non-adhesive condition. Thence,the potentially adhesive fibers are activated or made adhesive by theapplication of heat or suitable solvents or both. The fibrous mixturewith the potentially adhesive fibers in tacky condition is compressed tothe desired form and the adhesive fibers allowed to dry or harden to anon-tacky condition. The resulting compressed fibrous form is internallysupported by the bonding of the potentially adhesive fibers tothemselves and other fibers. It will be understood that throughout thefollowing specification and claims, the terms. non-adhesive andpotentially adhesive refer to types of fibers,

1' one of which becomes tacky or adhesive under conditions under whichthe other fiber is relatively unaffected. Where the tacky or adhesivecondition results from elevated temperature, the potentially adhesivefibers Will, of course, be of a thermoplastic nature. Ordinarily, thenon-adhesive fiber will not be thermoplastic but a thermoplastic fibercould be used provided the temperature at which it became tacky issufficiently higher than the temperature at Which the other potentiallyadhesive fiber becomes tacky. By way of example, the potentiallyadhesive fibers are formed from vinyl resins resulting from thepolymerization of compounds containing the vinyl group such aspolyvinylchloride or copolymers of vinyl chloride and vinyl acetate.Other potentially adhesive fibers, however, may be used successfully inthe present invention, for example, certain copolymers of vinyl chlorideand acrylonitrile.

Referring now to the drawings wherein preferred embodiments of myinvention are shown, Figure 1 shows the fibrous element in bundle orsliver form. As seen therein, the sliver A is a carefully blendedmixture of non-adhesive regenerated cellulose fibers such as rayonstaple and potentially adhesive or thermoplastic fibers. The fibersmentioned above are of the textile fiber class having diameters of atleast 9 microns.

The mixture of the present invention can be satisfactorily formed byuniformly distributing 10-25% of the potentially adhesive fibers intothe major proportion, 75-90% by Weight, of crimped rayon staple fiber.It has been found that the potentially adhesive fibers should compriseat least 10% by weight of the mixture and preferably should be in therange of 10-15% by weight.

The length of the individual fibers, both potentially adhesive andnon-adhesive, may vary from to 2 /2 inches and should be between 1 to 2/2 denier, preferably 1 to 1 /2 denier. Due to the crimp in thenon-adhesive fibers and, if desired, in the potentially adhesive fibers,minute traps or voids are formed within the body of the element whichenhance the absorptivcness of the element and also provide for theporosity which in turn permits easy draw. 1

The fibers specified above range in weight from 100-125 grains and thefine relatively short length fibers provide a compact, densestructure'in which many of the shorter length fibers will lie across thegeneral longitudinal axis of the element.

An important feature of my invention is that the nonadhesive or rayonfibers within the fibrous mass are crimped. In the case of rayon, thefibers may be crimped chemically .as distinguished from a mechanicalcrimp. Such chemical crimping is disclosed and claimed in United StatesPatent 2,517,694. This crimping remains in the fiber even when it iswet. The filaments, however, may be mechanically crimped according towell known processes and apparatus. Since relatively small denier fibersare used to form the element and since the fibers are crimped, numerousminute traps or voids are formed within the element which render thefibrous element capable of entrapping and retaining liquids, moistureand minute solid particles. The potentially adhesive fibers may or maynot be crimped. When converting the fibrous sliver A to specificarticles of use, the potentially adhesive fibers are activated, as willbe explained hereinafter, to autogenously bond together the non-adhesivefibers in the sliver A. The fibers are compressed, as will also beexplained, after the potentially adhesive fibers have been activated toprovide a compact article of good strength.

A tobacco smoke filter or plug B formed from the fibrous mass or sliverA of Figure 1 is shown in Figure 2 of the drawing. The tobacco smokefilter B, in this instance, is of cylindrical shape. The potentiallyadhesive fibers have been activated and compressed to autogenously bondtogether the non-adhesive rayon fibers and the potentially adhesivefibers to provide a compact cylindrical shaped article of good strength.When the completed element is to be used as a cigarette filter, thebonded element is wrapped or stuffed in a paper wrapper 2 and cut intosuitable lengths to form the filter plug B.

Figure 3 shows the wrapped filter plug B of Figure 2 incorporated in acigarette C. The tobacco and the filter plug B are formed into a unitarycigarette having the usual cigarette paper 11.

The interrelationship of the fibers making up the fibrous structure isshown in detail in Figure 3A of the drawing. As seen therein, thecrimped non-adhesive fibers, generally designated as D, D, are bonded tothe non-crimped adhehive fibers E, E at points of fiber intersection G,G. Some of the shorter fibers identified as F lie crosswise of thelongitudinal axis of the filter element. The short fibers F may be ofeither the crimped non-adhesive fibers D, D or the potentially adhesivefibers E, E.

The apparatus for forming and converting the mixed sliver to a tow orrod from which filter elements can be cut has been designed to insure acombination of all the desired properties for a cigarette filter. Such afilter element must have firmness or body, maximum filtering ability andporosity to permit free and easy draw. As is well known in the filterart, density of the filter is directly proportional to the pressurerequired to force the fiuid through the filter. Stated conversely, gooddraw which is, of course, low pressure is inversely proportional tofiltering ability or filter density. In the present filter andapparatus, it has been possible to obtain maximum filtering andabsorbing properties without increasing the density to the point wherethere is an objectionable lack of draw. The crimped fibers which areautogenously bonded into a uniform element with the minor proportion ofeither crimped or uncrimped potentially adhesive fibers cooperate toprovide this unexpected and desired result.

The apparatus in which the relatively loose sliver is activated andtransformed into a comparatively strong, dense but porous rod comprisesa chamber or tube 18 into which the sliver 19 is drawn through a funnelshaped die 20 mounted in the forward end wall 21 of the chamber. Thetacky sliver is drawn out of the chamber 18 through a relatively longerdie 23 mounted in the rear wall 24 of the chamber in alignment with die20. Die 23 has a substantially smaller bore than entrance die 20. Thepreferred diameters for the entrance and exit dies are and of an inchrespectively when it is desired to fabricate a cigarette filter. Forother articles the dimension of the bores may be changed butsubstantially the same ratio be maintained. The inside of the chamber 18is maintained at an elevated temperature of approximately 110 C. bymeans of one or more heating elements 25, 25 which surround the walls ofthe chamber. If desired, the heating elements are covered by suitableinsulating material 27 through which electrical connections to theheaters may be made at 28, 28. At a point approximately midway betweenthe downstream terminus of die 20 and the upstream terminus of die 23, aliquid softening or activating agent such as acetone is introduced intothe chamber through a nozzle 30. The acetone may fall directly on thesliver in the chamber or it may be vaporized when it falls onto theheated chamber wall. In either event the potentially adhesive orthermoplastic fibers in the sliver are sufficiently softened throughoutthe sliver so that when the sliver is drawn through die 23 there is acompression or rearrangement of the structure to provide a firm,cornpact, internally bound but porous tow or rod 31. The adhesive fibersset up after leaving die 23 when they are cooled and the acetoneevaporates or is otherwise removed. Partial setting up may take place inthe bore of die 23 and the length and relative axial position of thisforming die in the end wall 24 is controlled to provide the resultswhich may be desired. In order to eliminate sticking or deposition ofmaterial in the bore of either of the dies, they are preferably made ofpolytetrafiuoroethylene, sold commercially under the trade name ofTeflon.

Depending upon the degree of activation found desirable and the speedwith which the sliver is drawn through chamber 18 by means of draw rollsR, R, it may be found necessary or desirable to provide limited ventingfor the chamber. This can be accomplished by the provision of one ormore flats 35, 35 (Figure 5) along the side of the entrance die 20.These flats extend through the end wall 21 so that limited venting ofthe interior of chamber 18 is achieved. By providing an annular bevel 40on the downstream end of die 20, it is possible to prevent build-up oradherence of fibers to any part of die 20.

When the activated sliver is to be used for tobacco smoke filters, therod 31, after leaving the chamber 18,

rear 56* is folded around the rod 31. The wrapper 55 is sealed byapplying an adhesive from a liquid adhesive applicator 60 connected withan adhesive supply container 61 The diameter of the bore of the wrappingapparatus; 50 through which the activated sliver passes is some whatsmaller than the diameter of the exit die 23 of the chamber 18 wherebythe diameter of the tow is; further reduced to correspond with thediameter of a cigarette or tobacco cylinder with which the filter plug Bisto be incorporated; Vaporized acetone as an activating agent for thepotentially adhesive fibers is preferred in that it has been found thatthe fibers within the sliver 19 which have been subjected to vaporizedacetone are more firmly bonded together and the finished filter plugexhibits greater stifim ss with excellent draw properties. It has alsobeen found that a very clean cut may be made with the ace tone activatedfilter plug. In the apparatus described above, the softening of thepotentially adhesive fibers is" achieved primarily by means of thesolvent, namely, acetone, which is applied to the fibers. However, itwill be understood that the temperature in chamber 18 may besufficiently elevated to assist or, if desired, completely provide forthe softening ofthe minor proportion fibers;

Another important feature of my invention is that the filteringefficiency of a tobacco smoke filter improves during use. An inherentproperty of viscose. rayon is that it swells considerably when incontact with water or moisture. When my filter is. incorporated with acigarette, the filtering action improves as the tobacco burns since therayon fibers swell when contacted by the moisture carried by the smoke.The smoke components or ingredients which have been filtered out by thebase portion of the tobacco cylinder will therefore be more effectivelyfiltered out by the swollen fibers as. the base portion of the tobaccocylinder burns.

Various colored fibers may be used in the filter to provide a variety ofcolor schemes for the filter. The dye. pigment matter may beincorporated with the filament' forming spinning solution. Undyed'extruded filaments, from which the staple is cut, may be dyed by passingthe filaments through suitable dye baths.

If desired, aromatics such as perfume or menthol may be incorporatedwith the filter material to provide a filter having a pleasing aroma. Inaddition, other desired or essential oils may be incorporated with thefilter.

My tobacco smoke filter plug is porous and has excellent draw propertieswhich permit the smoker to easily pull the smoke through the filter. Thefilter is economical to produce and has sufiicient strength and firmnessto permit normal processing of the filter when manufacturing cigarettesor other tobacco smoking arti cles. As explained above, the filter plugcontains many minute voids or traps because fine denier fibers are usedand because the fibers are crimped. The traps easily catch and retainthe vapor and solid components of the smoke passing therethrough.

My fibrous element has numerous uses since it has good liquid andmoisture retention properties. Among the uses is that of dental salivapads which are placed within the patients mouth to absorb excess saliva.Tampons may also be produced from my fibrous absorptive element. Thefibrous element may also be used in other fields of medicine and surgerywherein liquid retentive pads are required.

It is to be understood that changes and variations may be made withoutdeparting from the spirit and scope of the present invention as definedin the appended claims.

Having thus described my invention, I claim:

1. An absorbent porous filter element consisting of a uniform mixture ofbonded together fibers comprising crimped non-adhesive fibers, andadhesive fibers, said non-adhesive crimped fibers being capable ofpermanently retaining their crimpv in either a dry'or wet condition.

2. An absorbent porous filter element according; to

claim} 1. wherein the adhesive fibers comprise at least 1-0 of theelement-by weight.

3-. An absorbent, porous filter element having uniform rigiditythroughout and consisting of a uniform mixture of bonded together fiberscomprising crimped non-adhesive staple fibersand adhesive fibers, saidadhesive fibers comprising at least 10% of the element by weight, saidnon-adhesive crimped fibers being capable of permanently retaining theircrimp' in either adry or wet condition.

4. An absorbent, porous filter element having uniform rigiditythroughout and consisting of a uniform mixture of bonded together fiberscomprising crimped, non-adhesive staple fibers and potentially adhesivefibers which have been activated, said potentially adhesive fiberscomprising at least 10% of the element by weight and the fibers being to2 /2 inches in length, said non-adhesive crimped fibers being capable ofpermanently retaining their crimp in either a dry or wet condition.

5. An absorbent, porous filter element having uniform rigiditythroughout and consisting of auniform mixture of bonded together fiberscomprising crimped 1 to 2 /2 denier non-adhesive .staple fibers to 2 /2inchesin length and potentially adhesive 1 to 2 /2 dlenier textilefiberswhichlhave: been activated, said potentially adhesive fiberscomprising at least 10% of the element by weight and being to. 2 /2inches in length, said non-adhesive crimped fibers being capable ofpermanently retaining their crimp in either a dry or wet condition.

6: An absorbent, porous filter element having uniform rigiditythroughout and consisting of a uniform mixture of bonded together fiberscomprising crimped viscose rayon. fibersand' at least 10% by weight offibers formed from copolymers of vinyl chloride and vinyl acetate whichhave been activated, said crimped viscose rayon fibers being capable ofpermanently retaining their crimp in either a dry or Wet condition. 7

7. An absorbent porous filter element having uniform rigidity throughoutand consisting of a uniform mixture of crimped non-adhesive staplefibers and adhesive fibers, at least some of said staple fibers beingbonded to some adhesive fibers, said adhesive fibers comprising at least10% of said porous element by weight, said non-adhesive crimped fibersbeing capable of permanently retaining their crimp in either a dry orwet condition.

8. An absorbent porous filter element having uniform rigidity throughoutand consisting of a uniform mixture of crimped non-adhesive fibers andactivated potentially adhesive fibers all of which are to 2 /2 inlength, at least some of said non-adhesive fibers being bonded to someadhesive fibers, said potentially adhesive fibers comprising at least10% of the element by weight, said nonadhesive crimped fibers beingcapable of permanently retaining: their crimp in either a dry or wetcondition.

9. An absorbent porous filter element having uniform rigidity throughoutand consisting of a uniform mixture of crimped non-adhesive staplefibers. and activated potentially adhesive fibers all of which fibersare to 2%" in length and of 1 to 2 /2 denier, at least some of saidstaple. fibers being bonded to some adhesive fibers, said potentiallyadhesive fibers comprising at least 10% of the element by weight, saidnon-adhesive crimped fibers being capable of permanently retaining theircrimp in either a dry or wet condition.

10. An absorbent porous filter element having uniform rigiditythroughout and consisting of a uniform mixture of crimped viscose rayonfibers and activated potentially adhesive fibers formed from copolymersof vinyl chloride and vinyl acetate, at least some of said rayon fibersbeing bonded to some adhesive fibers, said potentially adhesive fiberscomprising at least 10% of the element by weight, said crimped viscoserayon fibers'being capable of per.- manently retaining their crimp ineither a dry or Wet condition.

1.1 As an article of manufacture, a tobacco smoke a compressed mass of auniform mixture of crimped nonadhesive fibers and activated potentiallyadhesive fibers of staple length, at least some of said non-adhesivefibers being bonded to some adhesive fibers, said potentially adhesivefibers comprising at least 10% by weight of the filter, said crimpednon-adhesive fibers being capable of permanently retaining their crimpin either a dry or wet condition.

12. As an article of manufacture, a tobacco smoke filter having uniformrigidity throughout and comprising a compressed mass of a uniformmixture of crimped nonadhesive fibers bonded to staple length,potentially adhesive fibers which have been activated, said non-adhesivecrimped fibers being capable of permanently retaining their crimp inboth a dry and wet condition.

13. A tobacco smoke filter according to claim 11 having a paper wrapperaround the filter.

14. A tobacco smoke filter according to claim 11 com prisingnon-adhesive and potentially adhesive fibers of to 2% inches in length.

15. A tobacco smoke filter according to claim 11 comprising non-adhesiveand potentially adhesive fibers of 1 to 1 /2 denier.

16. A tobacco smoke filter according to claim 11 wherein thenon-adhesive fibers comprise viscose rayon fibers and the potentiallyadhesive fibers comprise fibers formed from copolymers of vinyl acetateand vinyl chloride.

17. As an article of manufacture, a tobacco smoke filter cylinder ofuniform rigidity throughout comprising a compressed mass of a uniformmixture of 75 to 90% by weight of the filter of crimped non-adhesivefibers and 10 to by weight of activated potentially adhesive fibers,at'least some of said non-adhesive fibers being bonded to some adhesivefibers, said non-adhesive crimped fibers being capable of permanentlyretaining their crimp in either a dry or wet condition.

18. As an article of manufacture, a filter type cigarette comprising atobacco cylinder, a filter cylinder at one end of the tobacco cylinder,and a cigarette paper wrapper around the filter cylinder and the tobaccocylinder, said filter cylinder comprising a compact porous mass ofuniform rigidity throughout and formed of a uniform mixture of crimpednon-adhesive fibers bonded to staple length, potentially adhesive fiberswhich have been activated, said non-adhesive crimped fibers beingcapable of permanently retaining their crimp in both a dry and wetcondition.

19. As an article of manufacture, a filter type cigarette comprising atobacco cylinder, a filter cylinder adjacent one end of the tobaccocylinder, and a cigarette paper wrapper around the filter cylinder andthe tobacco cylinder, said filter cylinder comprising a compact, porousmass of uniform rigidity throughout and formed of a uniform mixture ofcrimped non-adhesive fibers and staple length activated potentiallyadhesive fibers, at least some of said non-adhesive fibers being bondedto some potentially adhesive fibers, said potentially adhesive fiberscomprising at least 10% by weight of the filter cylinder, saidnon-adhesive crimped fibers being capable of permanently retaining theircrimp in either a dry or wet condition.

20. A filter type cigarette according to claim 19 wherein the filtercylinder comprises non-adhesive and potentially adhesive fibers of A; to2% inches in length.

21. A filter type cigarette according to claim 19 wherein the filtercylinder comprises non-adhesive and potentially adhesive fibers of 1 to2 /2 denier.

22. A filter type cigarette according to claim 19 wherein thenon-adhesive fibers of the filter cylinder comprise viscose rayon fibersand the potentially adhesive fibers comprise fibers formed fromcopolymers of vinyl'chloride and vinyl acetate.

23. As an article of manufacture, a filter type cigarette comprising atobacco cylinder, at filter'cylinder adjacent one end of the tobaccocylinder, and a cigarette paper filter cylinder comprising a compactporous mass of uniform rigidity throughout formed of a uniform mixtureof to by weight of crimped non-adhesive fibers and 10 to 25 by weight ofactivated potentially adhesive fibers, at least some of saidnon-adhesive fibers being bonded tosome adhesive fibers, saidnon-adhesive crimped fibers being capable of permanently retaining theircrimp in either a dry or wet condition.

24. A filter type cigarette according to claim 23 wherein thenon-adhesive fibers'comprise viscose rayon fibers and the potentiallyadhesive fibers are formed from copolymers of vinyl chloride and vinylacetate.

25. An absorbent, porous filter element having uniform d rigiditythroughout and consisting of a uniform mixture of bonded together fiberscomprising crimped non-adhesive staple fibers and uncrimped adhesivefibers which'have been activated, said adhesive fibers comprising atleast 10% of the element by weight, said non-adhesive crimped fibersbeing capable of permanently retaining their crimp in either a dry orwet condition.

26. As an article of manufacture, a tobacco smoke filter having uniformrigidity throughout and comprising a compressed mass of a uniformmixture of crimped non-adhesive fibers and staple length uncrimpedactivated potentially adhesive fibers, at least some of the nonadhesivefibers being bonded to some potentially adhesive fibers, the potentiallyadhesive fibers comprising at least 10% by weight of the filter, saidnon-adhesive crimped fibers being capable of permanently retaining theircrimp in either a dry or wet condition.

27. As an article of manufacture, a filter type cigarette comprising atobacco cylinder, a filter cylinder adjacent one end of the tobaccocylinder, and a cigarette paper wrapper around the filter cylinder andthe tobacco cylinder, said filter cylinder comprising a compact porousmass of uniform rigidity throughout and formed of a mixture of crimpednon-adhesive fibers and staple length noncrimped activated potentiallyadhesive fibers, at least some of the non-adhesive fibers being bondedto some potentially adhesive fibers, the potentially adhesive fiberscomprising at least 10% by weight of the filter cylinder, saidnon-adhesive crimped fibers being capable of permanently retaining theircrimp in either a dry or wet condition.

28. An absorbent, porous elongated element having uniform rigiditythroughout and consisting of a uniform mixture of bonded together fiberscomprising crimped 1 to 2 /2 denier non-adhesive staple fibers to 2%inches in length and at least 10% by weight of potentially adhesivefibers of 1 to 2 /2 denier and to 2% inches in length which have beenactivated, a portion of said shorter fibers lying widthwise of thelongitudinal axis of the element, said non-adhesive crimped fibers beingcapable of permanently retaining their crimp in either a dry or wetcondition.

References Cited in the file of this patent UNITED STATES PATENTS2,126,422 Tarrant Aug. 9, 1938 2,164,702 Davidson July 4, 1939 2,252,999Wallach Aug. 19, 1941 2,357,392 Francis Sept. 5, 1944 2,459,804 FrancisJan. 25, 1949 2,476,582 Browne et al. Jan. 19, 1949 2,483,406 FrancisOct. 4, 1949 2,688,380 MacHenry Sept. 7, 1954 2,707,308 Taylor et al.May 3, 1955 2,707,690 Janecke May 10, 1955 2,708,982 McGufi et al May24, 1955 OTHER REFERENCES The Modern Textile Dictionary by G. E. Linton.Pages 642-643. Published 1954 by Duell, Sloan and Pearce Little, Brownand Co., Boston, Mass.

1. AN ABSORBENT POROUS FILTER ELEMENT CONSISTING OF A UNIFORM MIXTURE OFBONDED FIBERS COMPRISING CRIMPED NON-ADHESIVE FIBERS, AND ADHESIVEFIBERS, SAID NON-ADHESIVE CRIMPED FIBERS BEING CAPABLE OF PERMANENTLYRETAINING THEIR CRIMP IN EITHER A DRY OR WET CONDITION.